a fatal disease of horses recorded in Queensland, Australia in 1994. A virus of the Paramyxoviridae family, genus Henipavirus that infects horses and humans and experimentally guinea pigs and cats. Clinical signs in horses include fever, dyspnea, copious, clear or blood-tinged, frothy nasal discharge, death in 1 to 3 days, with a case fatality rate of 60-70%. Necropsy lesions include pulmonary congestion and edema and acute interstitial pneumonia. The zoonotic infection originates from fruit-eating macrobats (Pteropus spp.) present in Eastern Australia. See equine henipavirus (below). In one fatal human case the clinical syndrome resembled in general that observed in horses while in a second case death occurred after a prolonged clinical course including signs of central nervous system dysfunction one year after infection.

a virus which in morphology and nucleotide sequence is similar to morbilliviruses and parainfluenza virus. The virus causes fatal illness in horses and humans following 'natural' infection, and of guinea pigs and cats following experimental inoculation. See acute equine respiratory syndrome (above). Previously called equine morbillivirus.

equine herpesvirus 1 (EHV1)

the major cause of equine viral abortion (see also equine viral abortion) and a myeloencephalitis. The latter is characterized by nervous signs varying from mild ataxia to enforced recumbency. Also causes respiratory disease (rhinopneumonitis), but the distinctly different equine herpesvirus 4, is more commonly identified as the cause of rhinopneumonitis and rarely abortion. A paralytic syndrome also occurs but usually in horses that are reinfected or, in a few instances, have been vaccinated. The disease may be a transitory incoordination or a permanent recumbency necessitating euthanasia. The virus may also cause viremia in newborn foals, the foals showing severe mental depression—sleepy foals.

equine herpesvirus 2 (EHV2)

a very common infection of horses, often asymptomatic but also associated with a variety of signs including pharyngitis, malaise and coughing. Formerly called equine cytomegalovirus or slowly growing equine herpesvirus, but now known to be a gammaherpesvirus 2 genus.

is caused by a nononcogenic retrovirus in the subfamily Lentivirinae. After an initial acute attack of fever, weakness to the point of incoordination, jaundice, petechiation of the mucosae and conjunctivae and ventral edema, there are alternating periods of normality and illness that may continue for many years. During ensuing attacks there is a gradual development of anemia, emaciation and cardiac insufficiency. The disease is contagious to all Equidae and is spread by biting flies and mosquitoes. Spread by veterinary equipment has occurred frequently in the past.

infectious equine bronchitis

see equine influenza (below).

equine influenza

an infectious disease of the upper respiratory tract of horses of all ages, and caused by members of the family Orthomyxoviridae, genus A. The identified viruses are influenza A/Equi Prague/56 (H7N7) and A/Equi-2/Miami/63 (H3N8). The clinical signs typical of the infection are a minor fever and a persistent, long-term cough which prevents the horse being exercised. Droplet infection is highly effective and the disease has the capacity to reach epidemic proportions quickly and disrupt racing and other equine activities. The course is about 3 weeks and there are usually no serious sequelae if the horse is cared for properly. Formerly called with some uncertainty also equine infectious bronchitis, Hoppengarten cough, laryngotracheobronchitis, shipping fever. Effective inactivated vaccines are available although the duration of protective immunity to infection is short. The viruses do not show the same degree of antigenic change (drift and shift) evident in human influenza A viruses.

firm subcutaneous nodules 0.5 to 5 mm diameter on the side of the neck, withers and back. They are eosinophilic granulomas and the cause is not known.

equine papular dermatitis

a transient skin disease of horses which may be caused by a virus. Begins with 0.25 to 1 inch diameter papules which subsequently crust over and then become alopecic. A number of horses are likely to be affected at the one time and an insect vector is suspected.

(formerly equine rhinovirus 1) member of the genus Aphthovirus, family Picornaviridae, causes an upper respiratory tract infection in horses with laryngitis and a copious sometimes purulent nasal discharge accompanied by viremia.

equine rhinitis B viruses

(formerly equine rhinoviruses 2 and 3) members of the genus Erbovirus, family Picornaviridae, causes upper respiratory tract infections in horses.

equine sarcoid

a common transplantable cutaneous neoplasm in horses. The cause is unknown but similar lesions can be caused by the intracutaneous injection of bovine papilloma virus. Lesions are hairless fibroid tumor masses that frequently ulcerate, look like large warts, often recur after excision, and occur most commonly on the lower legs but can occur on any part of the body. See also sarcoid.

all aspects of equine medicine which touch on quality of performance by show, event or racing horses; particular attention paid to diseases of the respiratory, cardiovascular and musculoskeletal systems.

equine staphylococcal dermatitis

a contagious but low prevalence equine dermatitis from which Staphylococcus aureus can be isolated regularly. Small, painful nodules appear under the harness; subsequently become pustular and rupture. Called also saddle scab, tail pyoderma.

a member of the family Arteriviridae, genus Arterivirus, causes this acute, severe infection of the upper respiratory tract of horses of all ages. Clinically the disease is more severe than the URTIs, the signs including abortion, conjunctivitis with edema of the conjunctiva, spasm of the eyelids and a profuse discharge. Coughing is severe and there is edema of the legs and ventral abdominal wall.

Conjunctivitis in equine viral arteritis. By permission from Knottenbelt DC, Pascoe RR, Diseases and Disorders of the Horse, Saunders, 2003

predominantly caused by equine herpesvirus 4. Occasionally this virus has caused abortion, but EHV1 is the predominant cause of abortion. The rhinopneumonitis is manifested by a cough, serous nasal discharge, mild conjunctivitis and fever. Abortion, when it occurs, does so in the last few months of pregnancy and the mare is not systemically ill at that time.

Patient discussion about equine

Q. Is the arthritis horses have the same as the arthritis people have?

A. To some extent yes, but not absolutely. In general, animals are widely used as models for diseases in humans. The basic process of arthritis (i.e. inflammation of the joints) is quite similar, although the causes, manifestations and results of this process may vary greatly.

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